Cutlass bearings

[Guest]

My boat is now out of the water for a prop/antifoul jobbie but whilst I have access to it I thought I should check the shaft end bearings.

Your advice please...
How is a cutlass bearing normally made up, is it a rubber mounted plain bronze bush type of support bearing?
How do you know when it is worn out - will simply shaking the propshaft for rattle be good enough?
Should there be just a minimum running clearance, like say, a "thou" or two?

Many thanks
Bernard

 

[miket]

Hold prop' in 2 hands and try to move shaft up/ down and side to side. Any excessive movement is bad.

Cutlass bearing consists of bronze alloy tube with ridges (logitudanal) of heavy duty rubber/ composition that surround the shaft. Idealy there should be no play.

I think I am correct in saying you are at Shamrock Q. If so am down tonight. John Blake and Dot are also down for weekend. John is off duty but I am sure would check the bearing. He did one of mine (Shiverarn) earlier this year. Right B******d it was too.

 

[Guest]

Shamrock

If it was good enough for Shiverarn........!
I'm hoping to get down there tomorrow and would welcome John Blake's opinion.
Please tell him to feel free to give Hexie's props a shake but watch out for the ragged edges!

Thanks for the info.

Regards
Bernard

 

[Guest]

A few points re cutlass bearings:

The most wear will be at the after end of the cutlass bearing, most likely caused by "whip" of the prop shaft because the prop is out of balance. You mention sharp jagged edges on the prop blades. This breakdown may be caused by softening of the bronze through anti-fouling of the prop, for example. Never AF the prop, as it causes the metal to go soft and reddish.

Remove the propellor and have it balanced. This usually costs a bit of area off the prop, but it has to be done. Sometimes a new prop is the only answer to achieve quieter smooth motoring.

Larger yachts sometimes have an extra cutlass bearing just aft of the stern gland / stuffing box. These can be very frustrating to deal with, and sometimes require the removal of the engine to get at. Check for wear and hopefuly leave well enough alone!

The bearings are typically constructed of ribbed rubber making a tight fit to the shaft, with bronze or sometimes that 70s fibre (whose brand name I cannot think of right now) on the outside. There are a multitude of metric and imperial sizes available, so make sure you measure the original carefully. Contact Mike Bellamy of Lancng Marine for a replacement. He is the king!

The bearing is often held into the housing by one or two grub screws buried under the anti-foul.

Please note that sometimes it is as cheap to buy the entire bearing AND housing. This may be the better option if you have damaged the housing getting the old bearing out. Good strong tools and localised heat are usually required to remove the originals.

A tough job, but worth the effort. You will find that you can comfortably use 300 to 400 more RPM, without your brain going numb.

Courage.

Tuscair.

 

[Guest]

Thanks

Many thanks for your help, I can't detect much movement at all in the bearings so I think I'll opt for leaving well alone!

My vibration clearly mainly comes from damaged props so I'll attend to that bit first.

Bernie

 

[miket]

Re: Shamrock

Duly tested. Perfect.

Was the other prop' in better or worse condition!
There must be special Bronze alloy eating fish in the Itchen.
What happened?

 

[Guest]

Shiverarn

Miket, thanks for the check, if you would let me have your personal Email address I'll tell you the story...

bernard.bowler@virgin.net

 

[miket]

Re: Shiverarn

m.thomas@macmillan.co.uk.

Sounds interesting!

Mike.